Preparation and magnetic properties of Ni-Co-P-Ce coating by electroless plating on silicon substrate

Ni-Co-P-Ce coating was prepared on Si substrate by electroless plating method under different Ce2(SO4)3 concentration, Ni2 +/Co2 + ratio and pH value, and then annealed under different annealing temperature. The surface morphology, thickness, composition, structure and magnetic properties of coatings were observed and determined by scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDX), X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM). With the increasing of Ce2(SO4)3 concentration in plating bath, the thickness and saturation magnetization of Ni-Co-P-Ce coating are firstly increased and then decreased. The thickness of coating is raised linearly with the increase of Ni2 +/Co2 + ratio and pH value, whereas too high pH value will deteriorate the plating bath and reduce the adhesion between substrate and coating. The saturation magnetization of Ni-Co-P-Ce coating is improved initially and then reduced with the promotion of Ni2 +/Co2 + ratio, pH value and annealing temperature. The optimum plating conditions and annealing temperature for Ni-Co-P-Ce coating are Ce2(SO4)3 concentration of 50 mg/L, Ni2 +/Co2 + ratio of 7/3, pH value of 9.0, and annealing temperature of 400 °C. The role of Ce element in the plating is to benefit the deposition of Ni ions, promote the formation of Ni(Co) phase during the annealing process, and thus improve the magnetic properties of Ni-Co-P-Ce coating.